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The work offers a comprehensive evaluation on the phylogenetics and conservation of splicing patterns of the plant SPF30 splicing factor gene family. In eukaryotes, one pre-mRNA can generate multiple mRNA transcripts by alternative splicing (AS), which expands transcriptome and proteome diversity. Splicing factor 30 (SPF30), also known as survival motor neuron domain containing protein 1 (SMNDC1), is a spliceosomal protein that plays an essential role in spliceosomal assembly. Although SPF30 genes have been well characterised in human and yeast, little is known about their homologues in plants. Here, we report the genome-wide identification and phylogenetic analysis of SPF30 genes in the plant kingdom. In total, 82 SPF30 genes were found in 64 plant species from algae to land plants. Alternative transcripts were found in many SPF30 genes and splicing profile analysis revealed that the second intron in SPF30 genome is frequently associated with AS events and contributed to the birth of novel exons in a few SPF30 members. In addition, different conserved sequences were observed at these putative splice sites among moss, monocots and dicots, respectively. Our findings will facilitate further functional characterization of plant SPF30 genes as putative splicing factors.

Rhizosheath comprises soil that adheres firmly to roots. In this study, two ecotypes of switchgrass with different rhizosheath sizes after drought stress were analyzed which showed metabolic differences under drought conditions. The rhizosheath comprises soil that adheres firmly to roots by a combination of root hairs and mucilage and may aid in root growth under soil drying. The aim of this work is to reveal the potential metabolites involved in rhizosheath formation under drought stress conditions. Panicum virgatum L. (switchgrass), which belongs to the Poaceae family, is an important biofuel and fodder crop in drought areas. Five switchgrass ecotypes (cv. Alamo, cv. Blackwake, cv. Summer, cv. Cave-in-Rock and cv. Kanlow) have a broad range of rhizosheath weight under drought conditions. For two selected ecotypes with contrast rhizosheath weight (cv. Alamo and cv. Kanlow), root hair length and density, lateral root number, root morphological parameters were measured, and real-time qRT-PCR was performed. Gas chromatography mass spectrophotometry (GC–MS) was used to determine the primary metabolites in the shoots and roots of selected ecotypes under drought stress conditions. The change trends of root hair length and density, lateral root number and related gene expression were consistent with rhizosheath weight in Alamo and Kanlow under drought and watered conditions. For root morphological parameters, Alamo grew deeper than Kanlow, while Kanlow exhibited higher values for other parameters. In this study, the levels of amino acids, sugars and organic acids were significantly changed in response to drought stress in two switchgrass ecotypes. Several metabolites including amino acids (arginine, isoleucine, methionine and cysteine) and sugars (kestose, raffinose, fructose, fucose, sorbose and xylose) in the large soil-sheathed roots of Alamo and Kanlow were significantly increased compared to small or no soil-sheathed roots of Alamo and Kanlow. Difference in rhizosheath size is reflected in the plant internal metabolites under drought stress conditions. Additionally, our results highlight the importance of using metabolite profiling and provide a better understanding of rhizosheath formation at the cellular level.